1. Field of the Invention
The present invention relates to semiconductor devices and manufacturing methods thereof, and more particularly to a semiconductor device having a conductive layer as an interconnection layer and a manufacturing method thereof.
2. Description of the Background Art
Conventionally, aluminum is used for an interconnection layer of a semiconductor device. The problem related to a method of manufacturing the interconnection with aluminum will be described.
FIGS. 18 to 22 are cross sectional views shown in conjunction with the problem associated with the conventional manufacturing method.
Referring to FIG. 18, an interlayer insulating film 102 is formed on a silicon substrate 101. A titanium nitride film 103 as a barrier layer is formed on interlayer insulating film 102. An aluminum film (hereinafter referred to as a high-temperature aluminum film) 105 is formed on titanium nitride film 103 by sputtering at a high temperature of about 400.degree. C.
The formation of the aluminum film at such high temperature increases planarity of high-temperature aluminum film 105. A crystal grain size of high-temperature aluminum film 105 is larger than that of an aluminum film formed at a low temperature. Therefore, when high-temperature aluminum film 105 is cooled, a recess 106 is formed by the grain boundary, for example, due to shrinkage of a crystal.
Referring to FIG. 19, an anti-reflection film 109 of titanium nitride is formed on a surface of high-temperature aluminum film 105. At the time, a thickness of anti-reflection film 109 is particularly small at a corner 106a of recess 106.
Referring to FIG. 20, resist is applied onto anti-reflection film 109. After the resist is exposed to light, a resist pattern 110 is formed by development using developer. As the thickness of anti-reflection film 109 is small at corner 106a of recess 106, the developer melts a portion of anti-reflection film 109 and also a portion of high-temperature aluminum film 105. Thus, recess 106 extends and an opening 107 is formed. Opening 107 is greater than the opening at anti-reflection film 109.
Referring to FIG. 21, etching of anti-reflection film 109 and high-temperature aluminum film 105 is started using resist pattern 110 as a mask. At the time, etch residue 111, formed by reaction of high-temperature aluminum film 105 and etchant, is left at a portion covered by anti-reflection film 109 in opening 107. It is relatively difficult to etch etching residue 111.
Referring to FIG. 22, when etching is further performed, etch residue 111 acts as a mask to leave high-temperature aluminum film 105 and titanium nitride film 103 thereunder. As a result, interconnection layers 112 and 113 are formed and, at the same time, residues 121 and 122 including conductive portions are formed at portions which would have essentially been free of such conductive materials.
Formation of an interlayer insulating film on residues 121 and 122 would result in insulation failure of the interlayer insulating film and reduction in reliability of the semiconductor device.